Researchers at Pacific Northwest National Laboratory have imaged two never-before-seen chemical intermediates that have been proposed to play key roles in the interconversion of oxygen and water on catalyst surfaces (J. Phys. Chem. C, DOI: 10.1021/jp807030n). The study broadens understanding of surface reaction mechanisms in photocatalyzed H2O splitting and other reactions of H2O and O2 on solids. . . .